The invention relates to a valve arrangement comprising a valve carrier, on which a plurality of control units are mounted with a mounting side to the fore and alongside each other, such control units each having a valve unit with a valve communicating in a sealing manner with fluid ducts in the valve carrier and furthermore having at least one electrically operated valve drive serving for the actuation of the valve.
A valve arrangement of this type is disclosed for instance in the European patent publication 0 608 245 B1. This known valve arrangement is provided with a plate-like valve carrier, which on a component mounting side is provided bearing a plurality of adjacently placed control units. The control units are constituted by valve units, each respectively comprising a valve and an electrically operated valve drive. The valves communicate with fluids ducts extending in the valve carrier and are in the position of supplying connected loads with pressure medium in a manner dependent on the controlled operation of the valve drives.
If such known valve arrangement is employed in the foodstuff and/or medical industry sector, particular problems arise as regards cleaning external surfaces of the valve arrangement. For reasons of hygiene extreme cleanliness must be observed here, but difficulties however arise because liquids and also solid materials collecting in the crevices and interstices present can hardly be dealt with. As a rule liquid cleaning devices such as high pressure cleaners are utilized to attempt to wash out the dirt. However in this case there is the problem that aggressive cleaning agents also penetrate into the interior of the valve unit, where they may cause damage. Furthermore corrosion damage or contamination of the foodstuffs may occur in connection with any residues of cleaning materials not removed.
One object of the invention is to create a valve arrangement of the type originally mentioned particularly suitable for environments involving intensive use of cleaning materials.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention the control units each comprise a liquid-tight casing body in which the components of the associated valve unit are jointly accommodated and which is mounted at the mounting side in a sealing manner on the valve body so that a liquid-tight, encapsulated individual accommodation of the individual valve units is provided.
The result is thus a valve arrangement also suitable for use in environments involving intensive application of cleaning materials, that is to say more especially for applications in the foodstuff, medical and semiconductor sectors. Due to the liquid-tight encapsulation of the valve units effective steps are taken to see that with application of sprayed cleaning liquid under high pressure same does not come into contact with the valve unit and cause damage thereto. Because the casing body may be produced with a smooth surface, it can be readily cleaned and consequently offers no or hardly any point on which dirt or residues could collect. Because the valve units furthermore constitute individual control units, it is moreover possible to ensure that a single valve unit may be individually replaced if it should become defective without interfering with the remaining control units. In this respect one particular embodiment is more especially advantageous, in the case of which the control units constitute self-contained and coherent assembly units, which are able to be handled bodily, i.e. so that the valve units and the casing body and accordingly together with the attachment of the casing body can be handled and also the attachment of the casing body and the attachment of the associated valve unit takes place simultaneously, something which considerably facilitates handling.
Further advantageous forms of the valve arrangement in accordance with the invention will appear from the claims.
The casing bodies of the control units may for instance consist of a corrosion resistant metal and more particularly stainless steel. As regards the material and manufacture a particular structure has price advantages, whose casing body includes a plastic material, as for instance polypropylene material. This renders possible a rational manufacture as plastic molding in some other plastic manufacturing and shaping system.
In order to prevent dirt collecting and at the same time to ensure a reliable cleaning operation it is more particularly preferred to make the outer face of the casing body without any edges and to shape rounded features and any transitions between flat surface sections with radiuses of at least three millimeters. The structure is thus intentionally made without a sharp edges on which residues of the cleaning material might collect after intensive cleaning.
The casing body may at least in part be made translucent so that light signals, produced by the valve unit, are visible from the outside through the translucent zone. The valve unit may for example be provided with light emitting diodes, which indicate the state of operation so that in the present case reliable monitoring from the outside is possible without openings in the casing body being necessary for this purpose. The translucent zones can be integral components of the casing body.
It is in principle possible, more particularly in the case of a design of the casing body of plastic material, to mold the casing body directly on the valve unit so that the number of the intermediate spaces between the casing body and the valve unit may be very simply reduced to a minimum. It would be feasible as well to a have a design similar to a skin directly enveloping the valve unit.
On the other hand it may be an advantage, more particularly also to ensure protection against mechanical damage, for the casing body to be made as a dimensionally stable component. In any case it is an advantage for the control unit comprising a casing body and the valve unit accommodated therein, to constitute, as already mentioned, a common structural unit handled as such, which may be uniformly assembled and taken to pieces without entailing the taking to pieces of the individual components.
To provide a sealing connection between the casing body and the valve unit a bonded or welded join may be provided. It is however more especially convenient to place a seal in between. Such seal is preferably molded on the control unit and preferably on the casing body, something which may be provided for by injection molding in an extremely simple fashion.
More particularly when the casing body is a dimensionally stable structure, intermediate spaces may be present between the casing body and the valve unit. Furthermore such intermediate spaces can normally not be avoided between the individual components of the valve unit. In such a case it may be an advantage for such intermediate spaces in the interior of the casing body to be at least partially and preferably completely filled with a filling material. It is in this manner that great variations in temperature, which are due to the application of the valve, may take place without water condensing, which would impair operation. The filling composition is preferably placed in the cavities by a injection molding operation or by foaming.
The filling composition may if required also perform an attachment function and serve to secure the valve unit in the interior of the casing body. Here the filling composition may constitute the sole attachment means so that no further attachment means, such as screws, are necessary to ensure the coherence of the casing body and the valve unit.
The seal acting between a control unit and the valve carrier is preferably an integral component of the filling composition so that the filling of the cavities may be performed like molding the seal as part of a common manufacturing process. All in all a twin component molding method is suitable, in which firstly the casing body is molded using a first plastic material into which in a further molding step, with the valve unit already integrated, the filling composition is introduced and simultaneously the seal is formed. This may take place in two separate injection molding devices or in a common injection molding device. It is possible firstly to mold the casing body and then to insert the valve unit and finally to inject the molding composition. It would however also be feasible to place the valve unit as an inserted part in an injection molding mold and to inject the casing body around same, the body then being completed with the seal and if necessary with the filling composition.
As a filling composition a rubber material or an elastomeric material may be employed.
The casing body is preferably in the form of a hoodlike body, which is slipped over the valve unit and with its opening to the fore is mounted on the valve carrier.
Again for reasons of ease of cleaning it is an advantage for the outer surface of the casing bony to be so designed that the surface roughness is at the most 2.24 microns. This is normally in accordance with the German standard VDI-Richtlinie 3400 Class 27-30.
In order to ensure that the cleaning material can readily drain off and that dirt does not collect, the control units are preferably arranged with a spacing between them on the valve carrier, it being recommended to have a spacing apart of at least five millimeters.
The valve carrier will as a rule have fluid ducts opening through at least one end face, where they may be connected with fluid pipes serving for the supply and/or removal of the pressure medium, particularly compressed air. It is an advantage here for a smooth-surfaced terminating body to be mounted with a sealing effect on the respective end and in which bypass ducts are located which at one end communicate with the fluid ducts and at the other end communicate with a connection face, at which fluid ducts leading to other equipment may be connected and which is placed opposite to the mounting face of the valve carrier carrying the control units.
The outer face of the terminating body is preferably made without any edges and designed to enable optimum cleaning by having the transitions between any flat surface sections and the rounded surface sections made with a radius of at least one millimeter.
In order to ensure that the liquid cleaning material is able to freely drain away it is furthermore an advantage if the overall height of the individual casing bodies is reduced from one end to the other, a continuous it reduction in height being recommended so that there is a configuration which slopes down from one end to the other.